
export function base64_decode(str) {
  var c1, c2, c3, c4;
  var base64DecodeChars = new Array(
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57,
    58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6,
    7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
    25, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36,
    37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1,
    -1, -1
  );
  var i = 0, len = str.length, string = '';

  while (i < len) {
    do {
      c1 = base64DecodeChars[str.charCodeAt(i++) & 0xff]
    } while (
      i < len && c1 == -1
    );

    if (c1 == -1) break;

    do {
      c2 = base64DecodeChars[str.charCodeAt(i++) & 0xff]
    } while (
      i < len && c2 == -1
    );

    if (c2 == -1) break;

    string += String.fromCharCode((c1 << 2) | ((c2 & 0x30) >> 4));

    do {
      c3 = str.charCodeAt(i++) & 0xff;
      if (c3 == 61)
        return string;

      c3 = base64DecodeChars[c3]
    } while (
      i < len && c3 == -1
    );

    if (c3 == -1) break;

    string += String.fromCharCode(((c2 & 0XF) << 4) | ((c3 & 0x3C) >> 2));

    do {
      c4 = str.charCodeAt(i++) & 0xff;
      if (c4 == 61) return string;
      c4 = base64DecodeChars[c4]
    } while (
      i < len && c4 == -1
    );

    if (c4 == -1) break;

    string += String.fromCharCode(((c3 & 0x03) << 6) | c4)
  }
  return string;
}


export function utf16to8(str) {
  var out, i, len, c;

  out = "";
  len = str.length;
  for (i = 0; i < len; i++) {
    c = str.charCodeAt(i);
    if ((c >= 0x0001) && (c <= 0x007F)) {
      out += str.charAt(i);
    } else if (c > 0x07FF) {
      out += String.fromCharCode(0xE0 | ((c >> 12) & 0x0F));
      out += String.fromCharCode(0x80 | ((c >> 6) & 0x3F));
      out += String.fromCharCode(0x80 | ((c >> 0) & 0x3F));
    } else {
      out += String.fromCharCode(0xC0 | ((c >> 6) & 0x1F));
      out += String.fromCharCode(0x80 | ((c >> 0) & 0x3F));
    }
  }
  return out;
}

export function utf8to16(str) {
  var out, i, len, c;
  var char2, char3;

  out = "";
  len = str.length;
  i = 0;
  while (i < len) {
    c = str.charCodeAt(i++);
    switch (c >> 4) {
      case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7:
        // 0xxxxxxx
        out += str.charAt(i - 1);
        break;
      case 12: case 13:
        // 110x xxxx 10xx xxxx
        char2 = str.charCodeAt(i++);
        out += String.fromCharCode(((c & 0x1F) << 6) | (char2 & 0x3F));
        break;
      case 14:
        // 1110 xxxx 10xx xxxx 10xx xxxx
        char2 = str.charCodeAt(i++);
        char3 = str.charCodeAt(i++);
        out += String.fromCharCode(((c & 0x0F) << 12) |
          ((char2 & 0x3F) << 6) |
          ((char3 & 0x3F) << 0));
        break;
    }
  }

  return out;
}
